It is well known that the introduction of foreign bodies into the blood stream, for example, the polished metal surfaces of artificial heart valves, tends to cause the formation of blood clots which may break loose and embolize to various parts of the body. Such thromboembolic problems have led to the administration of anticoagulants to patients with artificial heart valves. The effects of these anticoagulants on the blood clotting mechanism cause difficulties in stopping the flow of blood through even a minor flesh wound. In addition, flexible plastic conduits are used for vascular graft purposes and such surfaces also are thrombogenic.
Attempts have been made to overcome the thromboembolic problems of polished metal heart valves by providing a porous fabric covering over blood-engaging metal parts. When such porous fabrics have been used for covering metal heart valve parts, pores of typical size 500 to 700 microns have been provided and some tissue ingrowth has been observed. While the fabric covering has resulted in a decreased incidence of thromboembolism, apparently due to the observed tissue ingrowth, such valves do suffer from other defects, notably wear of the fabric, causing cloth fragment embolism and chronic hemolytic anemia as a result of turbulence of the blood over disrupted fabric coverings.
To date, the prior art has been unable to provide a heart valve which not only overcomes the thromboembolic problems of a smooth metal surface but also does not exhibit the wear failure problem of the prior art fabric covered heart valves.